JP7761897B2 - Bagging sheet for VaRTM molding and VaRTM molding method - Google Patents

Description

The present invention relates to a bagging sheet for VaRTM molding that seals repair spaces during VaRTM molding, and a VaRTM molding method using the same.

In recent years, VaRTM (Vacuum assisted Resin Transfer Molding) has become a popular technique for repairing structures. In VaRTM, reinforcing fiber sheets are layered over the area of the structure to be repaired, and the stacked reinforcing fiber sheets are then covered with a film. The interior is then depressurized using a vacuum pump, and resin is injected to integrate the FRP (fiber reinforced plastic) with the structure, thereby repairing the structure.

For example, Patent Document 1 discloses an adhesive structure for attaching FRP material to a structure. In the adhesive structure of Patent Document 1, an adhesive layer made of a fiber-based base material and resin is interposed between the structure and the FRP material, with the adhesive layer extending beyond the edge of the FRP material. According to Patent Document 1, this configuration ensures a sufficiently high adhesive strength between the structure to be repaired or reinforced and the FRP material used as a reinforcing material, ensuring that the repair and reinforcement performance of the FRP material can be achieved in the structure.

International Publication No. 2018/199032

As mentioned above, when repairing a structure using VaRTM molding, a sealant is laid around the perimeter of the repair area, a reinforcing fiber sheet or similar is placed within the enclosed sealant area, and then a tube connected to a vacuum suction pump or resin pot is placed inside the bagging sheet. The area is then covered with a film (hereafter referred to as the bagging sheet), and the film is tightly attached to the structure with the sealant. If gaps form between the bagging sheet and the tube, the bagging sheet cannot be vacuumed and a sealed state cannot be maintained, resulting in a decrease in the quality of the reinforcement and reduced work efficiency, such as prolonged pump operation.

In addition, the reinforcing fiber sheets are thick, and the surface of the steel reinforcement becomes uneven because the tubes rest on them. For this reason, the size of the bagging sheet is made larger than the surface area to be evacuated, in order to alleviate the tension generated in the bagging sheet when evacuated and allow the bagging sheet to conform to the surface irregularities. In other words, the side length of the bagging sheet is made larger than that of the reinforced area. To achieve a sealed state, the side length is adjusted by making several folds in part of the side length of the bagging sheet to match the side length of the reinforced area. However, if gaps are created in these adjusted areas, a vacuum cannot be created and the sealed state cannot be maintained. Furthermore, if the side length position or length is inappropriate, the bagging sheet will be pulled by the tension generated when evacuated, causing minute peeling of the sealing material placed between the bagging sheet and the structure, making it impossible to maintain a sealed state.

In light of these issues, the present invention aims to provide a bagging sheet for VaRTM molding and a VaRTM molding method that can prevent gaps from occurring between the bagging sheet and the tube or in the bagging sheet side length adjustment area, efficiently create a vacuum inside the bagging sheet, improve work efficiency, and maintain the quality of the FRP material.

To solve the above problems, a typical configuration of the bagging sheet for VaRTM molding according to the present invention is a bagging sheet used to seal repair spaces during VaRTM molding. The bagging sheet has lines on it, and by using the lines as guides to fold the edges of the bagging sheet in the order of valley fold, mountain fold, and valley fold, it is possible to form ears at the installation positions of tubes for vacuum suction or resin injection. The "ears" may also be called "tabs."

In the above configuration, the bagging sheet is folded to form tabs. Tubes are then inserted into these tabs. Sealant tape is wrapped around the positions of the tubes that correspond to the tabs, increasing the thickness of the sealant tape. This prevents gaps from forming between the bagging sheet and the tubes, and seals the interior of the bagging sheet. This allows the interior of the bagging sheet to be efficiently evacuated, improving work efficiency.

In particular, the bagging sheet of the present invention has lines that indicate the positions where the selvages will be formed and, in turn, the positions where the tubes will be installed. By forming lines on the bagging sheet that serve as indicators for the selvages in this way, workers can easily grasp the positions where the selvages will be formed.

The above lines should be placed on at least two of the three folds: valley fold, mountain fold, and valley fold. In this way, if lines are placed on at least two of the three folds, the above-mentioned effect can be achieved.

In addition, by placing the sealant tape on the lines of the bagging sheet in advance, workability on site can be improved.

To solve the above problems, a typical configuration of the VaRTM molding method according to the present invention is characterized by the use of the VaRTM molding bagging sheet described above. The components and their explanations corresponding to the technical concept of the VaRTM molding bagging sheet described above are also applicable to the VaRTM molding method.

The present invention provides a bagging sheet for VaRTM molding and a VaRTM molding method that can prevent gaps from forming between the bagging sheet and the tube or at the edges of the bagging sheet, efficiently create a vacuum inside the bagging sheet, and improve work efficiency.

1 is a schematic diagram illustrating a VaRTM molding method according to an embodiment of the present invention. 1A and 1B are diagrams illustrating a bagging sheet according to an embodiment of the present invention. FIG. 10 is a diagram illustrating the attachment of a bagging sheet to a steel pipe.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific values shown in these embodiments are merely examples intended to facilitate understanding of the invention and, unless otherwise specified, do not limit the present invention. Furthermore, in this specification and drawings, elements having substantially the same function and configuration are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

Figure 1 is a schematic diagram illustrating the VaRTM forming method of this embodiment. In this embodiment, the steps of the VaRTM forming method will first be explained, followed by a detailed description of the bagging sheet 100. This embodiment also illustrates the case where the repair object is a steel pipe 10 shown in Figure 1. However, the repair object is not limited to this, and the VaRTM forming method of this embodiment can also be applied to the repair of other structures.

As shown in Figure 1, steel pipe 10 corrodes over time, and as the corrosion progresses, holes may appear (hereinafter, the holes will be referred to as openings 12). When repairing openings 12 in steel pipe 10 using the VaRTM forming method of this embodiment, the area around opening 12 is first cleaned and the surface is adjusted. A plastic film is then adhered to the area around opening 12 to seal the opening 12. Sealant tape 130 is then placed around the area to be covered and evacuated with bagging sheet 100. An adhesive layer sheet 20 is then applied over the plastic film, and a reinforcing fiber sheet 22 is then laminated on top of the adhesive layer sheet 20. Here, bagging sheet 100 may be used as the plastic film, but a film with a thickness of approximately 50 μm or more that will not deform in a vacuum is preferred.

Next, a peel ply 24 is laid on the reinforcing fiber sheet 22. A suitable example of the peel ply 24 is glass cloth coated with fluororesin. By laying the peel ply 24 on the reinforcing fiber sheet 22 in this way, the sheet that is later laminated on the peel ply 24 can be easily peeled off from the reinforcing fiber sheet 22. Note that if the resin diffusion sheet 26, described below, is left in place, installation of the peel ply 24 can be omitted.

Next, a resin diffusion sheet 26 is laminated on the peel ply 24. The resin diffusion sheet 26 is a net-like sheet that is provided to allow the resin, described below, to flow smoothly over the surface of the reinforcing fiber sheet 22. After the resin diffusion sheet 26 is laminated, a vacuum suction tube 30 and a resin injection tube 40 are placed on top of it. The vacuum suction tube 30 is connected to a suction pump (not shown). The resin injection tube 40 is connected to a resin tank 42 in which resin is stored.

After the vacuum suction tube 30 and resin injection tube 40 are installed, the bagging sheet 100 of this embodiment is placed on top of them. After the periphery of the bagging sheet 100 is sealed, the air inside the bagging sheet 100 is sucked out using a suction pump. This creates a vacuum inside the bagging sheet 100, and resin is sucked into the bagging sheet 100. If there are gaps between the bagging sheet 100 and the vacuum suction tube 30 and the resin injection tube 40 at the insertion points, the inside of the bagging sheet 100 cannot be quickly evacuated. Therefore, to prevent the formation of such gaps, the bagging sheet 100 is used in the VaRTM molding method of this embodiment.

Figure 2 is a diagram illustrating the bagging sheet 100 of this embodiment. Figure 2(a) is a plan view of the bagging sheet 100. Figure 2(b) is a partial perspective view of the bagging sheet 100 with ears 140 (tabs) formed. The bagging sheet 100 is used to seal the repair space in VaRTM molding.

The bagging sheet 100 shown in Figure 2(a) has two pairs of three lines. Of the two pairs of three lines, one pair of three lines 110 is attached to the installation position of the vacuum suction tube 30, and the other pair of three lines 120 is attached to the installation position of the resin injection tube 40. In addition, sealant tape 130 is attached to the edge of the bagging sheet 100 (including the lines 110 and 120 on the edge).

In this embodiment, ears 140 are formed on the bagging sheet as shown in Figure 2(b). More specifically, using the three lines 110 and 120 shown in Figure 2(a) as guides, the edges of the bagging sheet 100 are folded in the order of valley fold, mountain fold, and valley fold. This causes the sealant tape 130 to adhere to the inside of the bagging sheet 100 as shown in Figure 2(b), and ears 140 are formed at the installation positions of the vacuum suction tube 30 and the resin injection tube 40 on the bagging sheet 100.

Figure 3 is a diagram illustrating the attachment of a bagging sheet 100 to a steel pipe 10. Figure 3(a) shows a state in which a resin diffusion sheet 26 is laminated on a peel ply 24 of the steel pipe 10 to be repaired. The following explanation illustrates the case in which the bagging sheet 100 is installed on a resin injection tube 40, but the procedure for installing it on a vacuum suction tube 30 is similar.

In the VaRTM molding method of this embodiment, as shown in Figure 3(a), the resin injection tube 40 is fixed to the peel ply 24 using sealant tape 50. Next, the bagging sheet 100, which has ears 140 formed as shown in Figure 2(b), is attached to the steel pipe 10 so that the ears 140 are positioned at the position of the resin injection tube 40 as shown in Figure 3(b). As a result, the edges of the bagging sheet 100 are adhered to the steel pipe 10 with the sealant tape 130, and the resin injection tube 40 is inserted into the bagging sheet 100.

At this time, because the bagging sheet 100 has ears 140, the bagging sheet 100 is bent at a right angle next to the resin injection tube 40. This allows the bagging sheet 100 to be fitted to the corner of the resin injection tube 40 and the steel pipe 10 with little force, and no gaps are left next to the resin injection tube 40. Then, sealant tape 60 is wrapped around the resin injection tube 40 in the position corresponding to the ears 140 to increase its thickness. This seals the inside of the bagging sheet 100.

As explained above, in the bagging sheet 100 of this embodiment and the VaRTM molding method using it, tubes (vacuum suction tubes 30 and resin injection tubes 40) are inserted into the ears 140 formed by folding the bagging sheet 100. This prevents gaps from forming between the bagging sheet 100 and the tubes. This allows the interior of the bagging sheet 100 to be efficiently evacuated, improving work efficiency.

In particular, the bagging sheet 100 of this embodiment is formed with lines 110 and 120 that serve as indicators for the position where the selvedge 140 will be formed (see Figure 2(a)). This allows the worker to visually determine the position where the selvedge 140 will be formed.

In this embodiment, a configuration has been illustrated in which a pair is formed by three lines 110 and 120 that indicate the three folds (valley fold, mountain fold, valley fold), but this is not limited to this. For example, the ear 140 can be folded by drawing lines at the two valley folds, or by drawing lines at the mountain fold and one valley fold. In other words, as long as lines are drawn at at least two of the three folds (folds), the ear 140 can be formed and the above-mentioned effects can be achieved.

While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. It is clear that a person skilled in the art could conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

The present invention can be used as a VaRTM molding bagging sheet that seals repair spaces during VaRTM molding, and as a VaRTM molding method using the same.

10...steel pipe, 12...opening, 20...adhesive layer sheet, 22...reinforced fiber sheet, 24...peel ply, 26...resin diffusion sheet, 30...vacuum suction tube, 40...resin injection tube, 42...resin tank, 50...sealant tape, 60...sealant tape, 100...bagging sheet, 110...wire, 120...wire, 130...sealant tape, 140...selvedge

Claims (3)

In the bagging sheet that seals the repair space in VaRTM molding,
The bagging sheet has lines on it,
A bagging sheet for VaRTM molding, characterized in that by using the lines as indicators and folding the edges of the bagging sheet in the order of valley fold, mountain fold, and valley fold, ears are formed at the installation positions of tubes for vacuum suction or resin injection , and the tubes can be inserted into the ears . A bagging sheet for VaRTM molding according to claim 1, characterized in that the lines are applied to at least two of the three folds: valley fold, mountain fold, and valley fold. A VaRTM molding method characterized by using the bagging sheet described in claim 1 or 2.